Allergen immunotherapy and asthma: efficacy, safety, and other considerations

The efficacy of allergen immunotherapy (AIT) for allergic asthma is often debated despite multiple controlled trails and three meta-analyses that have established a significant effect on subjective and objective outcomes. Indications for AIT in allergic asthma include suboptimal control with medications, adverse effect of medications, and/or environmental control measures; patient's desire to avoid long-term pharmacotherapy; and presence of comorbid allergic conditions. Symptomatic asthma is a risk factor for AIT systemic reactions (SRs) and asthma should be controlled at the time of the AIT administration. The vast majority of studies in AIT for asthma have used single allergens although the majority of allergic patients in the United States are not monosensitized. There have been conflicting results in the limited number of studies that have investigated the effect of multiallergen AIT or as add-on therapy to asthmatic patients who are optimally controlled with medications and environmental controls. Several studies have suggested that AIT may prevent the development of asthma in subjects with allergic rhinitis and new allergen sensitizations. The recently updated Allergen Immunotherapy Practice Parameters lists possible prevention of asthma in patients with allergic rhinitis as one of the indications for AIT. Currently, subcutaneous immunotherapy is the only route with Federal Drug Administration approved formulations in the United States but sublingual immunotherapy is currently under investigation. This review examines the efficacy, safety, and preventive effects of these two routes of immunotherapy.